1. Field of the Invention
The present invention relates to filter assemblies. More particularly, the present invention relates to hybrid triple-mode ceramic/metallic microwave filters that are smaller and less costly than comparable metallic combline resonators.
2. Background of the Invention
When generating signals in communication systems, combline filters are used to reject unwanted signals. Current combline filter structures consist of a series of metallic resonators dispersed in a metallic housing. Because of the required volume for each resonator, the metallic housing cannot be reduced in size beyond current technology, typically 3-10 cubic inches/resonator, depending on the operating frequency and the maximum insertion loss. Furthermore, the metallic housing represents a major cost percentage of the entire filter assembly. Consequently, current metallic filters are too large and too costly.